While streaming music on-demand over the Internet has been tipped as the “next big thing” for a few years now, in 2011, online streaming services finally started to gain traction in the mainstream. Spotify, which had been making waves in Europe since 2008, launched Stateside this summer after years' worth of stalled negotiations with the major labels. Meanwhile, competing services like Grooveshark and Rdio, both of which had been available in the U.S. for some time, dug in their heels and continued to grow their respective userbases. By the end of the year, it seemed like the all-streaming, fully-mobile, largely free future of music that had been promised for so long was at last, just around the corner.

And yet, as significant as this shift in listening habits might be for the music industry, the streaming revolution may seem like little more than a software upgrade for the average listener. While it's true that these new services reduce the amount of friction we experience when attempting to listen to a certain song right this minute, the paradigm of how we experience music remains largely unchanged. We're still listening to music on the computer, or on our phones or in the car. All that's changed is that we no longer need to remember to sync our iPod before heading out the door.

That's not to say, however, that our listening habits didn't start to evolve in more subtle ways in 2011. Tight integration between online music services and social media networks become the norm rather than the exception this year, encouraging (and in some cases, forcing) casual listeners to make their music consumption habits as public as their party snapshots. And while there's nothing new about sharing, discussing and collectively experiencing music online (as anyone who's ever posted on a fanboard, participated in a darknet or 'scrobbled' their listening habits via Last.fm will tell you), in 2011, mainstream services started nudging even casual fans to share their tastes as a matter of course.

Admittedly, in at least one case it was more of a shove than a nudge. Spotify's ham-handed rollout of Facebook integration made headlines this September when the company started automatically posting listener's choices to their Facebook profiles without prior warning. At the same time, the service closed its doors to any new users without existing Facebook accounts. Following a massive backlash in which social media unsurprisingly played a large part (a deluge of comments aimed at the company's GetSatisfaction page and Spotify founder Daniel Ek's Twitter account led the charge), the company rescinded on the former while remaining firm on the latter. While the service now offers a "private listening" option for closet Celine Dion fans, new users are still required to sign in using their Facebook accounts. This dust-up doesn't seem to have scared off Spotify from the social realm, however--in addition to an increasingly cozy relationship with Facebook itself, the company recently announced an app platform that bears more than a passing resemblance to Facebook's. And despite all of the negative feedback, Spotify's newfound social streak seems to be paying off--in November, the company announced that it had added 7 million new users since rolling out its Facebook integration two months prior.

Spotify's competitors, while less aggressive on the social front, made similar moves in 2011. Rdio announced a deal with Facebook, Grooveshark launched a Facebook app, a Tinysong API for sharing on Twitter and a Wordpress plug-in and Last.fm revamped its Facebook and Twitter sharing tools while also announcing support for Spotify users. Even large technology companies began to dip their toes into social music sharing: Apple continued to support its largely unpopular Ping service while Google added Google+ sharing to its Google Music product. In the past, if you wanted to automatically share your tastes with others, you had to set up an account with Last.fm, download and install an additional piece of software and then hunt down a plug-in or script to sling that data from Last.fm to your social network of choice. In 2011, all you need to do is sign into one of the major streaming services using your Facebook credentials.

As usual, however, hardcore music fans remain at the forefront when it comes to sharing online. Among serious listeners, Turntable.fm -- a service that allows users to play DJ and spin tracks for others in discrete listening "rooms" -- was the most talked-about service of the year. This too wasn't exactly a new idea--a service called Cohearing (later, Mixapp) was providing nearly identical functionality as far back as 2008--but in 2011, online DJing was an idea whose time had arrived. While services like Turntable.fm remain niche at present, if history offers any indication, we're likely to see similar features pop up in mainstream products sooner rather than later (in the case of, Spotify, a listening rooms feature is already available).

As the act of listening to music becomes less and less private, we may eventually come to understand the habit of sharing music tastes online as the first step toward a new mechanism for music discovery. As previous channels for discovering new music begin to fade into the periphery, casual fans will increasingly look to their friends' listening habits for recommendations. And while this trend will only accelerate the fragmentation of mainstream music tastes, most would agree that our migration away from the mythical "monoculture" of the '90s was already in motion.

Inevitable as it might be, this transition won't necessarily be a smooth one, however. As online music services continue to figure out how best to integrate social features into their products, we're likely to see more Spotify-like gaffes, unless companies carefully consider their users' privacy expectations in their rush for social synergy. Streaming services would also do well to pay similar attention to their security mechanisms -- as more and more music services begin to store credentials for social networks, these services will increasingly become attractive targets for anyone looking to steal a few thousand user accounts. Finally, there's the fundamental problem with the streaming services themselves: their as yet unproven ability to provide artists with a significant amount of income. A number of independent artists have complained that Spotify plays have only resulted in "fractions of pennies" in revenue and some artists, including Coldplay, Mac Miller and the Black Keys, have chosen to eschew streaming services completely for their new releases.

None of these problems, however, are insurmountable and as streaming services begin to supersede traditional music distribution, it's likely that many of these issues will get ironed out. In all probability, social music discovery will lead to a greater diversity of tastes, more exposure for little-known acts and numerous avenues for discovering music that's tailored to your individual preferences. If the 2000s can be characterized as the decade in which we finally figured out online music distribution, the 2010s may well be the decade in which we do the same for online music discovery.